FIV (Feline Immunodeficiency Virus)

What FIV is NOT

Cat saying don't believe everything you hear
  • FIV is NOT easily passed between cats
  • FIV is NOT passed to humans
  • FIV is NOT passed to other species eg dogs
  • FIV is NOT Feline AIDS
  • FIV is NOT a death sentence for your cat

What FIV is

Cells stained under microscope

  • FIV is a virus that affects a cat's immune system slowly over a matter of years,
  • It was only discovered in 1986, but has been around for a lot longer.
  • FIV is a virus specific to cats and only cats. 
  • It cannot exist for more than a few seconds outside the body
  • It is normally transmitted by severe bites, but occasionally an infected mother cat can pass it to her kittens via her milk, or during mating.
  • FIV is most commonly diagnosed in cats 5-10 years old, especially feral, stray or free-roaming toms.
  • Feline AIDS is the terminal stage of immune system destruction that FIV causes, but may not occur for many years, and does not always develop at all before the cat develops some other condition leading to euthanasia.
  • FIV is in the same class of viruses as the human immunodeficiency virus (HIV), the causative agent of acquired immunodeficiency syndrome (AIDS) in people. It is a retrovirus ie it inserts itself into the cat's genes. 

How do Cats catch FIV?

  • The virus is not easily passed between cats – it does not pass via shared food bowls, water bowls, litter brushes, grooming equipment or toys.
  • It CAN be passed through blood transfusions, severe gum infection (which opens a gateway into the body), occasionally via a mother's milk to her kittens, but mostly through the kind of severe, infected bite wounds and abcesses normally only seen in free-roaming tom cats – or their victims if they are bully-cats.
    Kittens that do test positive for FIV should be tested after about four months because this may be a false positive from antibodies in their mother's milk – the kittens themselves may not actually have FIV at all.  New kittens positive for FIV should NEVER be destroyed on these grounds.
  • A well-cared for neutered cat of either sex, living in a stable home, and kept in at night, is very unlikely to come into contact with the virus.

How is FIV diagnosed?

FIV has no symptoms.  It is not likely that you would suspect that your cat has FIV.
The times when it is likely to be detected is if a cat has been with an organisation such as ours, where FIV screening is done routinely, or if your vet decides to run an FIV test as part of the care regime.
FIV infection is diagnosed via a blood test, which checks for antibodies that are produced in response to FIV infection.  If this indicates infection, the vet may then seek a more specialised analysis called a  "Western Blot" test is the next step. Once this test is positive, the cat is considered to be truly infected because occasionally false positives occur.

Is there a Vaccine or a Cure?

There are some vaccines around, but it is not clear how effective they are.  Many veterinarians believe that the side effects of what vaccines exist are worse than FIV. In addition, once a cat has been vaccinated, it will always test positive for FIV even though it does not actually have the virus.
There is no cure as such – once a cat is infected, it has it for life, even if it never develops a single symptom. Drugs developed for human AIDS seem to be too toxic for cats to tolerate and given that most FIV cats never display any symptoms at all, the "cure" would be worse than the disease.

How can I help my Cat avoid FIV?

Black cat in window with dark starry night outside


  • NEUTER YOUR CAT
    This is the single most useful thing you can do on many, many grounds including avoiding FIV.  Neutered cats seldom get involved in fights as they are low in the cat hierarchy.  If you have a male cat, then for sure get him neutered. 
  • Keep your cat indoors at night, because this is the most likely time for cats to fight
  • You could consider keeping your cat indoors all the tune.  This is relatively uncommon in the UK, but common in countries with dangerous native animals, or where cats are a problem with wildlife.  It takes a lot more effort to make a happy home for an indoor cat, but it can be done.
    Alternatively you could train your cat to walk on a harness and lead.  Many cats in other countries do learn this as a matter of course, so it is not impossible.  A cat that goes out under supervision will be safer than one that goes out at will, and you will have another activity to share with your cat, but in the UK many people feel this is against the essential nature of the cat
  • Keep a close eye on your cat's health.  If he has a lot of minor illnesses – snuffles, diarrhoea and so on - and he goes out and has had fights (whether as aggressor or as victim) leading to puncture wounds or abcesses, discuss the possibility of FIV with your vet.

Heathy cat saying this is the face of FIV

Help! My Cat has FIV!

Don't panic! There is no need to have your cat euthanased immediately. 

  • If you have other cats in your household, have them tested for FIV as well – you need to know which ones to watch for health issues in.  However, unless your cats fight seriously among themselves, it is unlikely that they will have been infected
  • If your cat is not neutered, have him done as soon as possible, and likewise for your other cats
  • Help your cat's immune system by ensuring that he has a healthy lifestyle, is regularly wormed and de-flead, and sees your vet regularly.  The healthier it is, the less likely it is to fall prey to other infections, and the lower the likelihood of progression to Feline AIDS.
  • Keep your cat indoors!  This reduces both the likelihood of spreading the virus to another cat, and also of picking up infections.
  • If you have cat insurance, you will need to notify the insurer.  Most insurers do cover FIV as a new condition. 

If you are yourself immune-suppressed, or if you cannot provide the conditions described below for your cat, then please contact a cat-rehoming organisation stating that your cat is FIV and that you cannot care for it.  FIV cats are obviously harder to rehome than healthy cats, but there are adopters who will take them. 

Caring for an FIV Cat

Vet and cat
Really, all that is required what any cat requires, and is pretty much the same as for a diabetic cat, or one with renal problems, or in fact any "special needs" moggy!

  • Healthy food – the concensus is that raw food is not recommended because it can contain parasites and germs that are no problem for a healthy cat but could be hard for a cat with a compromised immune system.
  • A comfortable, stable environment either entirely indoors, or in a very protected outdoors situation
  • Your companionship
  • Regular veterinary check-ups, at least twice a year, with blood and urine analysis to
  • Vaccinations (live vaccines are fine)
  • Parasite control – fleas, ticks, worms, mites
  • Immediate response to health issues – small things that would not be a problem for a young healthy cat should be thoroughly explored in any special needs or elderly cat.
  • Be aware that there is always a possibility that the disease may accelerate and you may have to make hard decisions.  This is true for all chronic conditions such as diabetes and chronic renal failure.  Enjoy the time while your cat is not displaying any symptoms and do what you can to give him the best possible chance of health.
  • Most catteries will board FIV cats because they already ensure cats do not mingle, and disinfect between residents.  However, be aware that an FIV cat can suddenly decline and die, through no fault of anyone.  If you have a catsitter in your own home instead, you should make sure they understand about FIV and that they should not hesitate to take your cat to the vet even for minor things while you are away,

Adopting an FIV cat

Two cats in a hammock

  • Most FIV cats do not actually display any symptoms at all, and live long, healthy lives.
  • However, they are carriers of the virus and so could potentially infect other cats.
  • The best situation for an FIV cat is to come into a stable home, with no other cats, where it lives mainly or completely indoors, but maybe has access to an outside exercise pen, or walks outside on a harness and lead.  In many ways this is similar to adopting a blind cat, where similar conditions are required for entirely different reasons.
  • If, for example, you live in an apartment or flat without outside access, but are prepared to make your home an interesting living environment for your feline companion, an FIV cat would be a more sensible choice than a cat that has previously been used to free-roaming.  If the cat your adopt is recently diagnosed and was previously free-roaming, it will have to adjust to an indoor lifestyle (which means that you must stay strong and not give in to the pleading to be allowed out that will go on for a while but eventually subside!), but if an owner is motivated to provide a good life for it, with regular veterinary are, vaccinations and so on,  then there is no reason that it will not live as long and happy a life as any other cat.
  • If you already have an FIV cat, you could still adopt another FIV cat provided the introduction is done carelully.  Ordinary territorial spats that new housemates use to sort out their relationship are very unlikely to compromise the health of either cat
  • HOWEVER, this is a virus that slowly attacks the immune system, so as with diabetic cats, you will need to be alert to even minor health issues, and get treatment for them as soon as possible. 
  • If you take on an FIV cat, and you want to take out cat insurance, you may have difficulty in insuring him for conditions resulting from his FIV status.  This varies by insurer, so you will need to look into what different companies offer.
  • The one warning here would be if you are yourself immune-suppressed.  Because an FIV cat may be more liable to secondary infections, some of which could be transferable to humans, having an FIV cat would be a health risk for you.

CP FIV Cat Rehoming Policy

If a cat is in good health and has tested positive by ELISA and has been confirmed positive by immunofluorescence or western blot (available from Glasgow University) then the question arises about whether or not it can be homed.  Each case will be different and the decision is best made by each individual fosterer, in conjunction with their veterinary surgeon.  However, the following guidelines may help:

  • Absolute honesty is essential.  No CP fosterer should ever knowingly re-home an infected cat without first informing the new owner.  These cats, with their impaired immune systems, need prompt veterinary treatment for even the most minor infection.  Where one might be tempted, with an ordinary cat, to say, "wait a day and see what happens," one should never do so with an FIV-positive cat.  It should always see a vat immediately.
  • A healthy, FIV-infected cat may live for many years - but then again, it may not.  This should be made clear to the new owner.
  • Whilst FIV is not a very infectious disease, it must be realised that it can spread to other cats.  FIV-positive cats should only be homed to households with no other cats, or with only other FIV-positive cats.
  • Kittens with FIV-positive mothers may give positive test results because of antibodies from their mother's milk.  FIV-positive kittens should never be euthanased and should be retested at 4 months old - when most will have become FIV-negative.  They can then be homed as normal cats.
Further Info: https://www.cats.org.uk/oxford/feature-pages/fiv-feline-immunodeficiency-virus